Joint.



JOINT. PPLOTION FILED MAR. 2, 1910. RENEWED API-11.5, 1912. 1,046,416. `Patented Dec.3,1912.

G. A. KRAUS.

PATENT OFFICE.

CHARLES A. KnAU-s, or NEWTON HIGHLANDS, MASSACHUSETTS.

JOINT.

' Specification of Letters Patent.

Patented Dec. 3, 1912.

Original application filed August'27, 1909, Serial No. 514,859. Divided and this application* led March 2, 1910, Serial No. 546,958. Renewed April 5, 1912. Serial No. 688,788.

To all whom it 'may concern:

Be it known that I, CHARLES A. KRAUS, a citizen of the United States, and resident of Newton Highlands, in the county of Middle- 'sex and State of Massachusetts, have invented new and useful Improvements in Joints, of which the following is a speciiication.

My invention relates to the construction of gas-tight joints between metallic members formed by means pf a'thermally and electrically insulating separator or4 intermediary, and the object of my invention is to produce effective joints of this type impervious to gases, capable of resisting t-he stresses due to mechanical shock and thermal changes, and also which shall possess in an effective degree the quality of electrical and thermal insulation. p 1

My invention consists in an-improved and special form of joints of this general character; other forms are described in an application for patent filed by me August 27,

1909, Serial No. 514,859, of which this application is a division.

The chief difliculties heretofore encountered in making such joints as are contemplated in connection with -my invention, are lack of intimate union between the surfaces of metals and the refractory insulating separator or intermediary and the liability of the intermediary to fracture by reason largely of differences in co-etiicient of thermal expansion and improper cooling.

By my invention herein to be described, thermally and electrically insulating joints between metallic .members may be made which are adapted to the conditions alluded to. f

The drawing hereto' annexed -illustrates sectionally a joint made according to my invention. l

Tubular metal members, A and C, are' joined to and connected by'an intermediate sleeve B, of refractory insulating material,

which fits the conical enlargements D, D,

" of the tubular members A and C. Oneof .these tubular members, C, in the example .In the construction of the joint, measures must be adopted to provide for an intimate union between the refractory intermediary and the metal surfaces in order that no leakage, however small, shall take place between the adjacent. members. When oxidizable metals, such as iron or steel, are employed, a considerable amount of oXid appears on their surfaces or is formed before the insulating member can be applied;and moreover, gases are almost invariably present in the metal itself, and these are given olf on heating the metal during the application of the insulating member. In order, therefore, to. correct these conditionswhich are hostile to the obtainment o-f a satisfactory result, before the intermediary member B is introduced between the metal surfaces, both these metal surfaces are heated 4 and coated with a relatively fusible vitreous material which with the metal is Aheated to such a temperature that the vitreous coating .becomes sufficiently fluid to readily dissolve tjhe oxid on the surface of the metal memers.

The readiness of fusibility of such a vitreous flux is, of course', relative and variable, and is defined with reference to the physical and structural character of .the ,metal members to which it is applied. Its fusibility should be such that it may be rendered yfluid and dissolve the`oxid at a temperature not so high as injuriously to affect the metal member itself. The process of solution of the oxid may be hastened byl suitable mechanical manipulation of the flux. While the process of fusing the vitreous coating and the dissolving of the metal oXid is goingon, gases are driven out of the walls of the metal and collect in bubbles` under the vitreous coating, but since this coating is fluid these bubbles escape through the 'vitreous material and a layer of the vitreous flux free from bubbles is intimatelyv I fused on the metal. In general, it will be found preferable to coat the metal surfaces with a layer of vitreous material which is more 4readily fusible than is the intermediary member, B, because in this way the necessary fluidity is obtained at a temperature sufficiently-low to facilitate the application of the membervv B. This member may, to be sure, in some instances, be made of material as readily fusible as the vitreous flux or coating, or may be of the same material, but it is preferableto employ a more refractory body for this separator or intermediary. One reason for this lies in the fact that the more readily fusible the intermediary the better as a rule will it conduct electricity. Then again, it is desirable that thev insulating .intermediary shall retain its form in the process of making the joints. Thus in making a joint like that shown in the drawing, the vitreous oXid-lux having been applied to the metal members, these members are united by pressure with the intermediary B between them. If this intermediary were readily fusible it would be liable in such process to be squeezed out of 4its proper place in the joint. `Also it is desirable to reduce as far as possible the temperature at which permanent stresses begin to appear, and by employing relatively easily fusible material in combination with the metal members and a more refractory separator, this temperature is reduced to that at which the more fusible material becomes substantially rigid or solid.

While it will often be found convenient to make the insulating intermediary B of glass, it may be found desirable in some cases to employ other materials, not homogeneous, with the oXid-flux. Thus a semivitreous or fritted material, as, for example, porcelain, lai/ite, magnesium oxid, etc., may be employed. If the material used is I' porous, it may be glazed so as to be impervious to gases.

For the manufacture of joints between iron or steel tubular members, Iprefer to employ for the intermediary sleeve or memis often desirable to employ I'recommend a vitreous composition containing 50 parts soda glass, 50 parts boraX, and 12 parts iron oXid, by weight. A vitreous composition of this character and substantially as specified, forms the subject matter of an application for patent, Serial No. 514,858, filed v by me August 27, 1909.

W'hat I claim and desire to secure by Letters Pate-nt is:

` 1. The combination of two metal members, an insulating intermediary joined thereto, the joint between the metal and the intermediary involving a low melting glaze in close adhesive association with the metal members and the intermediary, and an envelop of a materialv similar tothe glaze, fused around and embracing the entirejoint.

2. The combination of two tubular metal members, a refractory insulating intermediaryv joined thereto and connecting the metal members, a cup-like extension secured 

